Conventional bending presses known from the document WO 96/13346.
A bending press according to one embodiment described and illustrated in the document WO 96/13346 comprises a pair of carriages which can be moved along its movable blank-holder in order to rearrange its segments. Each of these carriages comprises a first set of teeth fixed to the carriage, an input shaft housed in the shoe-holder body and connected to the first set of teeth by a toothed sprocket, a second set of teeth fixed to the shoe, and gearing for transmitting the drive of the input shaft to the second set of teeth.
This known mechanism enables the movements of the two shoes to be coordinated with the movements of the movable blank-holder, preferably by numerical control, in a manner such that, for movements of the movable blank-holder away from the fixed blank-holder there are corresponding simultaneous movements of the two shoes towards the centre of the press and towards the fixed blank-holder, without sliding of the shoes on the sheet. The two shoes are returned to the position in which they are moved away from the centre of the press by means of respective spiral springs or equivalent means incorporated in the shoe-holder body and interposed between it and the input shaft of the mechanism.
The mechanism according to document WO 96/13346 represented considerable progress in comparison with the prior art but has the disadvantage of being expensive because of the precision required in the manufacture and assembly of its components, particularly of its sets of teeth and its toothed sprockets.